1. Field of the Invention
The present invention relates to aircraft landing gear wheels and more particularly to a device for rotating the wheels prior to landing and for disengaging the drive system after landing.
2. Description of the Prior Art
It is well known that landing of aircraft causes the wheels to slip and drag after contacting the ground before the wheels reach full speed of rotation and that such action rapidly wears the tire surfaces and may burn or strip rubber off of the tires. This problem is especially severe for commercial aircraft and military aircraft due to their size and weight. A number of attempts have been made to solve this problem but none of these appear to have been sufficiently practical so as to be generally adopted.
Examples of previous devices for this purpose may be found in such patents as U.S. Pat. No. 3,850,389 to Dixon, which teaches a variable speed motor that may be selectively engaged and disengaged from the wheel for rotating the wheel during flight and which disengages when the motor is turned off after landing. Ellsworth in U.S. Pat. No. 3,542,318 uses motors drivingly connected to the wheels which are automatically energized when the landing gear begins to lower prior to landing and which are turned off as soon as the gear is fully lowered. As may be noted, this system does not permit control of the wheel rotation to the point of landing. In U.S. Pat. No. 3,096,052, Hardigan discloses a device for prespinning aircraft landing wheels which utilizes a ground speed indicator to control the rate of rotation. A number of other patents have been issued in the United States in which this problem has been approached by providing vanes and the like attached to the wheels to utilize aerodynamic forces to cause rotation. In spite of this body of prior art, there is no known system presently available and in common use which provides a reliable device which can prespin the aircraft wheels prior to landing to a speed which will minimize scuffing and wear upon landing and which includes means for automatically disconnecting the driving system from the wheels at the moment of touchdown to obviate the dangers and problems which can occur when the driving system remains engaged.